The present application relates to apparatus for cleaning a moving paper web in general and particularly to cleaners which affect the boundary layer of air moving with the paper web.
In a typical web offset press an image to be printed is transferred to a rubber blanket which is brought into contact with a moving web of paper onto which the image is printed. Minute amounts of loose fiber and dust from the paper web stick to the rubber blankets so that over time the blankets become dirty and must be cleaned to maintain image quality. It has been found that the frequency with which the rubber printing blankets must be cleaned can be substantially decreased if the paper web is precleaned before it is printed upon. In my earlier patent, U.S. Pat. No. 6,178,589, which is incorporated herein by reference, I disclosed an apparatus for cleaning the web which used an old but effective type of web cleaning roll. This existing web cleaning roll consisted of a central steel core on which multiple disks of cloth were compressed to form the roll surface. The surface of the roll, i.e. the cloth material was frayed to form a soft outer surface which is then worn in against a moving web. To effectively clean the web, an interaction between the cleaning rolls is uniformly established with the boundary layer of air which attaches to a moving web. This boundary layer which attaches to the paper web is only a small fraction of an inch thick. An ordinary web cleaner using only vacuum to remove fibers and dust from a paper begins to be ineffectual as paper speeds increase above 800 feet per minute (13 fps) because the boundary layer of air which moves with the paper web becomes more difficult to penetrate.
The buffing rolls are operated at relatively high speeds and, because of space limitations and overall cost, are relatively narrow in diameter—typically between three-and-one-half inches and four-and-one-half-inches in diameter. The fabric rings of the prior buffing rolls were constructed with only relatively narrow diameter cores, for example about 1.5 inches in diameter for a buff diameter of 4 inches. The same buffing rolls typically have a length of between 20 and 60 inches. The construction of the prior art buffing rolls which employ a solid central steel core overlain with disks of cloth results in some difficulty in assuring proper balance so that the cleaning rolls do not vibrate. If the central core is made too large in diameter, it can be difficult for maintenance people to handle the cleaning rolls. Further, renewing the soft outer surface of the rolls requires returning the rolls to the factory with the added cost of shipping to and from the factory.
What is needed is a paper cleaning roll which is lighter, stiffer, and which has a surface which can be renewed more readily.